/* ==========================================================================
   Sakul Learning — Editorial design system (violet × green duotone)
   Hand-written CSS. No build step, no framework.
   Aesthetic: cool paper light / violet-black dark, green↔violet accents,
   high-contrast variable serif
   display (Fraunces), refined reading serif body (Newsreader), grain texture,
   generous spatial rhythm, nested "bezel" cards, custom-easing motion.
   ========================================================================== */

/* ---- Design tokens -------------------------------------------------------- */
:root {
  color-scheme: light dark;

  /* Light palette — violet × green duotone on cool paper */
  --paper:        #f6f5fb;
  --paper-tint:   #eceaf6;
  --ink:          #1b1a24;
  --ink-soft:     #45415a;
  --ink-faint:    #7b7790;
  --line:         #e3e0f0;
  --card:         #ffffff;
  --accent:       #7c3aed; /* violet */
  --accent-2:     #0e9f6e; /* green  */
  --accent-soft:  #b8a6f0;
  --grad:         linear-gradient(120deg, var(--accent-2), var(--accent));
  --code-bg:      #efedf9;
  --code-ink:     #5b3aa6;

  /* Curves & rhythm */
  --ease:         cubic-bezier(0.32, 0.72, 0, 1);
  --measure:      68ch;
  --shell:        min(46rem, 92vw);
  --radius:       1.4rem;
  --radius-inner: calc(var(--radius) - 0.4rem);

  /* Soft, diffused ambient shadow (no harsh black) */
  --shadow:
    0 1px 1px rgba(40, 30, 70, 0.05),
    0 8px 24px -12px rgba(40, 30, 70, 0.18),
    0 30px 60px -40px rgba(40, 30, 70, 0.32);
  --grain-opacity: 0.035;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper:       #0e0d16;
    --paper-tint:  #16131f;
    --ink:         #eae8f6;
    --ink-soft:    #bab5d0;
    --ink-faint:   #837f99;
    --line:        #272239;
    --card:        #16131f;
    --accent:      #a78bfa; /* violet */
    --accent-2:    #34d399; /* green  */
    --accent-soft: #5b4a99;
    --code-bg:     #1a1629;
    --code-ink:    #cbbdf3;
    --shadow:
      0 1px 1px rgba(0, 0, 0, 0.30),
      0 10px 30px -16px rgba(0, 0, 0, 0.55),
      0 40px 70px -45px rgba(0, 0, 0, 0.75);
    --grain-opacity: 0.05;
  }
}

/* ---- Reset & base --------------------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100dvh;
  font-family: "Newsreader", Georgia, "Times New Roman", serif;
  font-size: 1.18rem;
  line-height: 1.72;
  color: var(--ink);
  background-color: var(--paper);
  background-image:
    radial-gradient(120% 90% at 8% -10%, color-mix(in srgb, var(--accent-2) 16%, transparent), transparent 55%),
    radial-gradient(115% 95% at 100% 0%, color-mix(in srgb, var(--accent) 20%, transparent), transparent 52%),
    radial-gradient(90% 80% at 60% 120%, color-mix(in srgb, var(--accent-2) 10%, transparent), transparent 55%);
  background-attachment: fixed;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* Fixed film-grain overlay — atmosphere without hurting scroll perf */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  opacity: var(--grain-opacity);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='160' height='160'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  mix-blend-mode: overlay;
}

::selection { background: color-mix(in srgb, var(--accent) 28%, transparent); }

/* Visible keyboard focus everywhere (no element clears it without a replacement) */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 4px;
}
:focus:not(:focus-visible) { outline: none; }

/* Skip link — visually hidden until focused */
.skip-link {
  position: fixed;
  top: 0.75rem;
  left: 50%;
  transform: translate(-50%, -150%);
  z-index: 50;
  padding: 0.6rem 1.1rem;
  border-radius: 999px;
  background: var(--ink);
  color: var(--paper);
  font-family: "Fraunces", serif;
  font-size: 0.85rem;
  box-shadow: var(--shadow);
  transition: transform 0.3s var(--ease);
}
.skip-link:focus { transform: translate(-50%, 0); }

img { max-width: 100%; height: auto; }

/* ---- Typography ----------------------------------------------------------- */
h1, h2, h3, h4 {
  font-family: "Fraunces", Georgia, serif;
  font-weight: 560;
  line-height: 1.08;
  letter-spacing: -0.018em;
  color: var(--ink);
  font-optical-sizing: auto;
  text-wrap: balance;
}
h1 { font-size: clamp(2.4rem, 1.6rem + 3.6vw, 4rem); font-variation-settings: "SOFT" 0, "WONK" 1; }
h2 { font-size: clamp(1.7rem, 1.3rem + 1.8vw, 2.3rem); margin-top: 2.6em; }
h3 { font-size: clamp(1.3rem, 1.1rem + 0.8vw, 1.55rem); margin-top: 2em; }

p, ul, ol { max-width: var(--measure); }
p { margin: 0 0 1.25em; }

a {
  color: var(--accent);
  text-decoration: none;
  background-image: linear-gradient(currentColor, currentColor);
  background-size: 0% 1px;
  background-position: 0 100%;
  background-repeat: no-repeat;
  transition: background-size 0.4s var(--ease), color 0.3s var(--ease);
}
a:hover { background-size: 100% 1px; }

blockquote {
  margin: 1.8em 0;
  padding: 0.4em 0 0.4em 1.4em;
  border-left: 2px solid var(--accent);
  color: var(--ink-soft);
  font-style: italic;
}

hr {
  border: 0;
  height: 1px;
  margin: 3em 0;
  background: linear-gradient(90deg, transparent, var(--line) 20%, var(--line) 80%, transparent);
}

/* Eyebrow / pill tag */
.eyebrow {
  display: inline-block;
  font-family: "Fraunces", serif;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.22em;
  color: var(--accent-2);
  padding: 0.35em 0.9em;
  border: 1px solid color-mix(in srgb, var(--accent-2) 38%, transparent);
  border-radius: 999px;
  background: color-mix(in srgb, var(--accent-2) 9%, transparent);
}

/* ---- Layout shell --------------------------------------------------------- */
.container,
.site-footer-inner { position: relative; z-index: 2; }

.container {
  width: var(--shell);
  margin: 0 auto;
  padding: 4.5rem 0 6rem;
}

/* ---- Floating glass nav --------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  justify-content: center;
  padding: 1.1rem 1rem 0;
}
.site-header__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
  width: var(--shell);
  max-width: 100%;
  padding: 0.6rem 0.7rem 0.6rem 1.4rem;
  border-radius: 999px;
  border: 1px solid color-mix(in srgb, var(--ink) 9%, transparent);
  background: color-mix(in srgb, var(--card) 72%, transparent);
  -webkit-backdrop-filter: blur(10px) saturate(1.15);
  backdrop-filter: blur(10px) saturate(1.15);
  box-shadow: var(--shadow);
}
.site-title {
  font-family: "Fraunces", serif;
  font-weight: 600;
  font-size: 1.12rem;
  letter-spacing: -0.01em;
  color: var(--ink);
  background: none;
}
.site-title:hover { background: none; color: var(--accent); }
nav {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
}
nav a {
  padding: 0.45em 1em;
  border-radius: 999px;
  font-family: "Fraunces", serif;
  font-size: 0.92rem;
  color: var(--ink-soft);
  background: none;
  transition: background-color 0.35s var(--ease), color 0.35s var(--ease);
}
nav a:hover {
  background: color-mix(in srgb, var(--ink) 7%, transparent);
  color: var(--ink);
}

/* ---- Hero ----------------------------------------------------------------- */
.hero {
  margin-bottom: 4rem;
  padding-bottom: 0.5rem;
}
.hero h1 {
  margin: 0.4em 0 0.3em;
  max-width: 16ch;
  /* green → violet gradient text — the duotone signature */
  background: var(--grad);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
@supports not ((-webkit-background-clip: text) or (background-clip: text)) {
  .hero h1 { color: var(--accent); background: none; }
}
.hero p {
  font-size: 1.32rem;
  color: var(--ink-soft);
  max-width: 46ch;
}

/* ---- Section headings with index dot ------------------------------------- */
.section-label {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  margin: 0 0 1.8rem;
  font-family: "Fraunces", serif;
  font-size: 0.78rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--ink-faint);
}
.section-label::before {
  content: "";
  width: 7px; height: 7px;
  border-radius: 50%;
  background: var(--grad);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--accent) 18%, transparent);
}
.section-label::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--line);
}

/* ---- Post list as nested bezel cards ------------------------------------- */
.post-list { list-style: none; margin: 0; padding: 0; max-width: none; }
.post-list li {
  /* outer shell */
  padding: 0.5rem;
  margin-bottom: 1.1rem;
  border-radius: var(--radius);
  border: 1px solid color-mix(in srgb, var(--ink) 7%, transparent);
  background: color-mix(in srgb, var(--card) 55%, transparent);
}
.post-list a.post-card {
  /* inner core */
  display: block;
  padding: 1.6rem 1.8rem;
  border-radius: var(--radius-inner);
  background: var(--card);
  border: 1px solid var(--line);
  box-shadow: inset 0 1px 0 color-mix(in srgb, #fff 60%, transparent);
  color: inherit;
  transition: transform 0.5s var(--ease), box-shadow 0.5s var(--ease);
}
.post-list a.post-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow);
}
.post-card__title {
  font-family: "Fraunces", serif;
  font-size: 1.5rem;
  font-weight: 560;
  line-height: 1.15;
  letter-spacing: -0.015em;
  margin: 0.15rem 0 0.5rem;
  color: var(--ink);
}
.post-card:hover .post-card__title { color: var(--accent); }
.post-card__summary {
  margin: 0.4rem 0 0;
  color: var(--ink-soft);
  font-size: 1.05rem;
  max-width: 60ch;
}
time, .meta {
  display: inline-block;
  font-family: "Fraunces", serif;
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--ink-faint);
}

/* ---- Generic content surfaces -------------------------------------------- */
.page, .post { max-width: none; }
.post > header { margin-bottom: 2.5rem; }
.post > header .eyebrow { margin-bottom: 1.2rem; }
.post > header h1 { margin: 0 0 0.6rem; }
.summary {
  font-size: 1.3rem;
  line-height: 1.5;
  color: var(--ink-soft);
  max-width: 50ch;
  margin-top: 0.8rem;
}

/* article body width — keep prose to a comfortable measure */
.post > *:not(header):not(.sources),
.page > * { margin-left: auto; margin-right: auto; }

/* Sources block — set off as a card */
.sources {
  margin-top: 3.5rem;
  padding: 1.8rem 2rem;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--paper-tint);
}
.sources h2 { margin-top: 0; font-size: 1.25rem; }
.sources ul { padding-left: 1.1rem; }
.sources li { margin-bottom: 0.5rem; color: var(--ink-soft); }

/* ---- Code ----------------------------------------------------------------- */
code, pre {
  font-family: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, monospace;
  font-size: 0.9em;
}
code {
  background: var(--code-bg);
  color: var(--code-ink);
  padding: 0.12em 0.4em;
  border-radius: 6px;
}
pre {
  overflow-x: auto;
  padding: 1.25rem 1.4rem;
  margin: 1.8em 0;
  border-radius: var(--radius-inner);
  background: var(--code-bg);
  border: 1px solid var(--line);
  line-height: 1.6;
}
pre code { background: none; padding: 0; color: var(--ink); }

/* ---- Footer --------------------------------------------------------------- */
.site-footer {
  position: relative;
  z-index: 2;
  border-top: 1px solid var(--line);
  background: color-mix(in srgb, var(--paper-tint) 70%, transparent);
}
.site-footer-inner {
  width: var(--shell);
  margin: 0 auto;
  padding: 2.5rem 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem 1.5rem;
  justify-content: space-between;
  align-items: baseline;
}
.site-footer p { margin: 0; max-width: none; color: var(--ink-faint); font-size: 0.95rem; }
.site-footer .footer-mark {
  font-family: "Fraunces", serif;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--ink-faint);
}

/* ---- Floating Table of Contents (scrollspy) ------------------------------ */
.toc {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);
  /* sit in the right margin, just outside the centered article column */
  right: max(1.5rem, calc((100vw - var(--shell)) / 2 - 15rem));
  width: 13.5rem;
  max-height: 76vh;
  overflow-y: auto;
  z-index: 20;
  font-family: "Fraunces", serif;
  /* hidden until JS confirms there are enough headings + a wide-enough viewport */
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.4s var(--ease);
  -ms-overflow-style: none;
  scrollbar-width: none;
}
.toc::-webkit-scrollbar { display: none; }
.toc.is-ready { opacity: 1; visibility: visible; }

.toc__label {
  font-size: 0.66rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.22em;
  color: var(--ink-faint);
  margin: 0 0 0.9rem 0;
}
/* Hierarchical bulleted list: green discs for top-level (h2),
   violet hollow bullets for nested (h3). */
.toc ul { margin: 0; padding-left: 1.15rem; max-width: none; }
.toc > ul { list-style: disc; }
.toc ul ul { list-style: circle; margin-top: 0.1rem; padding-left: 1.05rem; }
.toc li { margin: 0.12rem 0; }
.toc li::marker { color: var(--accent-2); }
.toc ul ul li::marker { color: var(--accent); }
.toc a {
  display: inline-block;
  padding: 0.12rem 0;
  font-size: 0.88rem;
  line-height: 1.32;
  color: var(--ink-faint);
  background: none;
  transition: color 0.25s var(--ease);
}
.toc ul ul a { font-size: 0.82rem; }
.toc a:hover { color: var(--ink); }
.toc a.is-active { color: var(--accent); font-weight: 500; }
.toc li:has(> a.is-active)::marker { color: var(--accent); }

/* Anchored headings shouldn't hide under the sticky nav when jumped to */
.post h2[id], .post h3[id] { scroll-margin-top: 6rem; }

@media (max-width: 1180px) {
  .toc { display: none; }
}

/* ---- Motion: scroll reveal ----------------------------------------------- */
/* Content is visible by default. The hidden/animated start state is opted into
   only when JS is confirmed present (<html class="reveal-enabled">), so the page
   degrades gracefully with JS disabled, blocked, or failed. */
.reveal-enabled [data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition:
    opacity 0.5s var(--ease),
    transform 0.5s var(--ease);
  transition-delay: var(--reveal-delay, 0ms);
  will-change: transform, opacity;
}
[data-reveal].is-visible {
  opacity: 1;
  transform: none;
  will-change: auto;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }
  .reveal-enabled [data-reveal] { opacity: 1; transform: none; filter: none; }
}

/* ---- Responsive ----------------------------------------------------------- */
@media (max-width: 768px) {
  :root { --shell: 92vw; }
  body { font-size: 1.08rem; }
  .container { padding: 3rem 0 4rem; }
  .site-header__bar { gap: 0.6rem; padding-left: 1rem; }
  .site-title { font-size: 1rem; }
  nav a { padding: 0.4em 0.7em; font-size: 0.85rem; }
  .post-list a.post-card { padding: 1.3rem 1.3rem; }
  .hero p { font-size: 1.15rem; }
}